Mold for casting railroad car wheels



March 18, 1969 F. w. PONZAR MOLD FOR CASTING RAILROAD CAR WHEELS I of 2Sheet Filed Dec. 19, 1966 FIG] 0 WA Z N E O V P WW D E Du F BY we)?FIG.2

ATTORNEYS March 18, 1969 F. w. PONZAR MOLD FOR CASTING RAILROAD CARWHEELS Sheet 3 of2 Filed Dec. 19. 1966 METAL ZONE AT FEED SLOT 48 HEATSINK METAL NR m WP w D E R F ATTORNEYS United States Patent 3 ClaimsABSTRACT OF THE DISCLOSURE A mold for casting a railroad wheelcomprising a center core, a gate core reposing on the center core, and afloat core resposing on the gate core; and so arranged and formed inrelation to a riser opening in the mold as to facilitate completion ofthe hub opening of the wheel.

This invention relates to mold apparatus for producing railroad carwheels by foundry or casting procedures.

Railroad car wheels have been manufactured for many years from what isconventionally known as gray iron foundry techniques. These cast ironwheels were common in freight service until the railroads increasedtheir operating speeds and loads to a point where the properties of castiron were no longer satisfactory; and hence the use of steel becamenecessary. It was found, however, that merely substituting steel forcast iron would not produce satisfactory wheels, because certain basicdifferences between the two foundry practices revealed that practiceswhich produced sound cast iron wheels were not suitable for steel. Someof these problems had their origin in the fact that molten steel isconsiderably less fluid than cast iron. Raising the pouring temperatureof molten steel will improve its fluidity somewhat, but because of therelatively high shrinkage of steel, when it transforms from the liquidto solid state, higher pouring temperatures can cause unsoundness todevelop in heavy sections in castings. Stated otherwise, it has beenfound that lower pouring temperatures tend to produce less porosity insteel castings.

Another factor which was encountered was the difficulty engendered bythe geometry or configuration of the wheel. The conventional railroadcar wheel is a disc-like body having a heavy hub section containing acylindrical central aperture for receiving the axle, a relatively thinplate or web section and a relatively heavy rim or tread section. Thisshape, for practical considerations, requires that the location of thesprue or opening, whereby the molten metal is introduced into the moldcavity, should be coincidental with the rotational axis of the wheel andthat the wheel shall be cast in a substantially horizontal plane. Someof the problems which arose when more or less conventional rammed sandmold techniques were attempted were porosity in the tread section,porosity in the hub zone and a severe washing of the mold cavity duringthe pouring operation which tended to produce surface and dimensionaldefects. The mold apparatus comprising this invention solves theseproblems, among others.

It is therefore a principal object of this invention to provide animproved mold for the manufacture of sound cast steel railroad carwheels, characterized 'by a center core, a gate core, and a float coreassembled at the portion of the mold corresponding to the hub of thewheel and the riser opening through which molten metal is poured.

Briefly stated, and in accordance with one embodiment of this invention,a mold for casting such wheels is provided, including a gate core whichprevents slag and other non-metallic material from entering the moldcavity, and which controls the rate at which the mold cavity is filled,

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thereby preventing washing, and which feeds molten metal to the heavyhub section during solidification to prevent porosity from developing.

Other and further objects of the present invention will be apparent fromthe following description and claims and are illustrated in theaccompanying drawings which, by way of illustration, show a preferredembodiment of the present invention and the principles thereof and whatis now considered to be the best mode contemplated for applying theseprinciples. Other embodiments of the invention embodying the same orequivalent principles may be used and structural changes may be made asdesired by those skilled in the art without departing from the presentinvention.

In the drawings:

FIG. 1 is a sectional view of a mold constructed in accordance with thepresent invention;

FIG. 2 is a fragmentary sectional view on an enlarged scale of a portionof FIG. 1;

FIG. 3 is a plan view of the gate core; and

FIG. 4 is a schematic view showing an intermediate stage in the coolingand solidification of the casting.

With reference to FIG. 1 of the drawing, the invention is disclosed asembodied in a rammed sand foundry mold 10 comprising a cope 12 and drag14. Separating the cope and drag members is a chill member 16, forchilling the molten metal corresponding to the tread of the wheel. Itwill be understood that, as shown, the cope 12 and the drag 14 ispreferably right circular cylinders, while the chill 16 is essentially atruncated right circular cone. These features are well known in the art,and are here described for purposes of understanding. In fact, theinvention can be applied to the permanent car wheel mold disclosed inapplication Ser. No. 507,999, filed Nov. 12, 1965.

The mold cavity for casting the steel railroad car wheel is formed bythe rammed sand or equivalent foundry refractory material in the copeand drag members, as shown at 20 and 21, and by the chill 16. Thatportion of the mold cavity within which the hub portion of the wheel isformed contains a refractory assembly 3 0, which may conveniently bereferred to as a core; however, the functions performed by the coreassembly go far beyond those presented by the usual foundry core, aswill be shown presently.

The assembly of core 30 comprises a center core 32, a strainer or gatecore 34 and a cover or float core 36. As shown in FIGS. 1 and 2, centercore 32 is supported in a recess 38 in the rammed sand drag. It iscomposed of a solid, right circular cylindrical base portion 40 having acup-shaped cavity 41 formed therein, opening at the top of the coremember 32. The cavity 41 is defined by a vertical, annular wall 41Wpresenting an upper free edge 41E, FIG. 2. An external, annular shoulder408 is formed in base 40, being of larger diameter than the wall 41W.

The exterior of the center core represents the hub opening of the wheelto be cast.

The strainer or gate core 34 is essentially a cup-shaped circular dischaving a vertical rim portion 44 by means of which the core 34 issupported across the bottom of the pouring basin or riser cavity 46 inthe cope, as shown in FIG. 1. The bottom wall 34W of core 34 is providedwith a large central opening 48 and a plurality of smaller openings 50adjacent rim 44, FIG. 3. The bottom wall 34W of the core 34 is providedwith spaced fingers 34F each having a shoulder 348 at the underside,enabling the core to repose neatly on the upper edge 41E presented bythe wall 41W of the center core 40.

The float core 36 is essentially a solid, circular plate provided withrecessed shoulders 368 at the underside which rest upon the top surfaceof wall 34W of core 34, FIGS. 1 and 2, in such a manner as to completelyexpose opening 48 as well as the openings 50.

In use, the cope, drag, chill and core 3-0 are assembled together asshown. Clamping means, not shown, are provided to secure the cope 12 andchill 16 together and other clamping means (also not shown) are used tosecure the cope and drag together. Molten steel is then poured into theopening 46, constituting a central riser, so that the initial contact ofthe stream of molten metal is upon the float core 36. The molten metalflows over the top of core 36 and down through openings 50. The pouringis continued at a rate such that the riser 46 is filled quickly andmaintained substantially filled throughout the duration of the pouringoperation. The weight and the velocity of the molten metal above thefloat core 36 holds it in place over opening 48 and the plurality ofsmall openings 50 serve a metering and straining function which preventsslag and other relatively light impurities from entering the main moldcavity.

By thus restricting the rate at which the molten metal may enter themold cavity, splashing and turbulence are vastly reduced andobjectionable washing of the mold is avoided, thus contributing to animproved surface of the casting. Further, the interior of the moldcavity is filled at a constant, controlled or metered rate which is adesirable condition.

As the mold cavity is filled, the level of the molten metal approachesand ultimately reaches the feed opening 48, from whence it flows intoand fills the cavity 41, which becomes a heat sink toward whichcontraction of the casting takes place. Eventually, molten metal fillscavity 41 and contacts the lower surface of the float core 36. Pouringis terminated. At this time, cover core 36, which is made from arefractory material which is lighter than the molten steel, floats freeof core 34 and rises into opening 46, completely exposing opening 48.When core 36 reaches the surface of the molten steel in the sprue orriser 46, it serves the additional function of providing an insulatingheat barrier and helps keep the molten steel below it, especially thatin the heat sink 41, from losing heat too rapidly to the atmosphere.

On the other hand, the chill 16 promotes the rapid transfer of heat tothe atmosphere and hence a directional solidification pattern ispromoted which helps insure soundness in the tread and plate zones ofthe wheel casting and produces a desirable structure. Thus,solidification takes place first at the tread chill 1'6 and thenprogressively inwardly toward the hub. The last portion of the wheel tosolidify in the hub zone where the core assembly 30 is located, and allof the shrinkage attendant with the final solidification occurs at thatzone. However, the large volume of still molten metal in the pouringbasic or riser area 46, as well as that in the reservoir 41, isavailable to feed through the large opening 48 and the openings 50' tosupply molten steel to prevent shrinkage porosity in the hub zone. Bythese means, a thoroughly sound wheel is cast in which there issubstantially no slag and in which all the shrinkage is confined to theriser which is later twisted E and discarded as hereinafter described.

After about fifty-five minutes of cooling, the general state of thecasting, including the riser, is as shown schematically in FIG. 4. Themetal in the zones corresponding to the feed slot 48 and gate openingsis by no means completely solid at this time. The cope is lifted andtwisted slightly. This separates the riser and the heat sink metal inthe cavity 41, as well as the metal in zones 48 and 50, from whatconstitutes the hub of the wheel, generally along line SL, FIG. 4. Thecope is replaced to keep the wheel casting hot. After about one hour,the cope is completely removed, and the casting is ready for shake-out.

Resultantly, upon separation of the casting front the center core 32 andthe gate core 34, the hub opening is defined, and the metal in thecavity 41 is a mere slug or bob, already separated from the hub of theWheel.

Hence, while I have illustrated and described a preferred embodiment ofthe present invention, it is to be understood that this is capable ofvariation and modification.

I claim:

1. In a mold for casting a railroad wheel having a hub opening: acircular center core the outer diameter of which represents the diameterof said hub opening; said center core having a cavity formed therein,bounded by an upstanding wall, and which opens at the top of the centercore; a separate gate core reposing 0n the upper edge of said annularwall and having gate openings therein in communication with the portionof the mold cavity surrounding the exterior of said center core, saidgate core presenting a feed slot through which molten metal may flowinto said cavity; and a float core resting on the gate core and sodimensioned as to expose said gate openings and said feed slot.

2. A mold for casting railroad wheels comprising: a drag portion formedof a refractory mold material including a centrally located cylindricalcenter core which has an upwardly opening cup-shaped cavity therein; a.cope portion formed of a refractory mold material and being supportedupon said drag portion, said cope portion having a centrally locatedriser opening within which is supported a gate core provided with alarge central feed opening and a plurality of smaller aperturesoutwardly located of the central feed opening; and a float core formedof a refractory material having a lesser density than the metal to becast resting upon said gate core and exposing said gate openings andexposing said central feed opening to said cavity.

3. The mold of claim 2 in which said large central feed opening islocated above the cavity in said cylindrical core and said smallerapertures are located outwardly of said cylindrical core.

References Cited UNITED STATES PATENTS 106,243 8/ 1870 Wilmington 1643565 1,025,438 5/1912 West 164356 1,281,946 10/1918 Griffin 249-562,835,007 5/1958 Hoefer 164353 I. SPENCER OVERHOLSER, Primary Examiner.

EUGENE MAR, Assistant Examiner.

U.S. c1. X.R.

